Initial Type resolution for closures

This adds the type checking for a HIR::ClosureExpr which specifies a
TyTy::ClosureType whih inherits the FnOnce trait by default. The
specialisation of the trait bound needs to be determined by the the
mutability and argument capture and moveablity rules.

The CallExpr is amended here so that we support CallExpr's for all
receivers that implement any of the FnTraits. This means closures and
generics that have the relevant type bound of FnTraits we get the same path
of type checking.

Addresses #195

9 files changed, 479 insertions, 31 deletions

diff --git a/gcc/rust/hir/tree/rust-hir-expr.h b/gcc/rust/hir/tree/rust-hir-expr.h
index c3180d8..66d8509 100644
--- a/gcc/rust/hir/tree/rust-hir-expr.h
+++ b/gcc/rust/hir/tree/rust-hir-expr.h
@@ -2131,6 +2131,8 @@ public:
   };
   std::unique_ptr<Expr> &get_expr () { return expr; }
 
+  std::vector<ClosureParam> &get_params () { return params; }
+
   void accept_vis (HIRFullVisitor &vis) override;
   void accept_vis (HIRExpressionVisitor &vis) override;
 
diff --git a/gcc/rust/typecheck/rust-hir-type-check-expr.cc b/gcc/rust/typecheck/rust-hir-type-check-expr.cc
index aa044dd..8911a1d 100644
--- a/gcc/rust/typecheck/rust-hir-type-check-expr.cc
+++ b/gcc/rust/typecheck/rust-hir-type-check-expr.cc
@@ -178,16 +178,6 @@ TypeCheckExpr::visit (HIR::CallExpr &expr)
 {
   TyTy::BaseType *function_tyty = TypeCheckExpr::Resolve (expr.get_fnexpr ());
 
-  bool valid_tyty = function_tyty->get_kind () == TyTy::TypeKind::ADT
-		    || function_tyty->get_kind () == TyTy::TypeKind::FNDEF
-		    || function_tyty->get_kind () == TyTy::TypeKind::FNPTR;
-  if (!valid_tyty)
-    {
-      rust_error_at (expr.get_locus (),
-		     "Failed to resolve expression of function call");
-      return;
-    }
-
   rust_debug_loc (expr.get_locus (), "resolved_call_expr to: {%s}",
 		  function_tyty->get_name ().c_str ());
 
@@ -214,6 +204,24 @@ TypeCheckExpr::visit (HIR::CallExpr &expr)
 	  rust_assert (adt->number_of_variants () == 1);
 	  variant = *adt->get_variants ().at (0);
 	}
+
+      infered
+	= TyTy::TypeCheckCallExpr::go (function_tyty, expr, variant, context);
+      return;
+    }
+
+  bool resolved_fn_trait_call
+    = resolve_fn_trait_call (expr, function_tyty, &infered);
+  if (resolved_fn_trait_call)
+    return;
+
+  bool valid_tyty = function_tyty->get_kind () == TyTy::TypeKind::FNDEF
+		    || function_tyty->get_kind () == TyTy::TypeKind::FNPTR;
+  if (!valid_tyty)
+    {
+      rust_error_at (expr.get_locus (),
+		     "Failed to resolve expression of function call");
+      return;
     }
 
   infered = TyTy::TypeCheckCallExpr::go (function_tyty, expr, variant, context);
@@ -1422,7 +1430,123 @@ TypeCheckExpr::visit (HIR::MatchExpr &expr)
 void
 TypeCheckExpr::visit (HIR::ClosureExpr &expr)
 {
-  gcc_unreachable ();
+  TypeCheckContextItem &current_context = context->peek_context ();
+  TyTy::FnType *current_context_fndecl = current_context.get_context_type ();
+
+  HirId ref = expr.get_mappings ().get_hirid ();
+  DefId id = expr.get_mappings ().get_defid ();
+  RustIdent ident{current_context_fndecl->get_ident ().path, expr.get_locus ()};
+
+  // get from parent context
+  std::vector<TyTy::SubstitutionParamMapping> subst_refs
+    = current_context_fndecl->clone_substs ();
+
+  std::vector<TyTy::TyVar> parameter_types;
+  for (auto &p : expr.get_params ())
+    {
+      if (p.has_type_given ())
+	{
+	  TyTy::BaseType *param_tyty
+	    = TypeCheckType::Resolve (p.get_type ().get ());
+	  TyTy::TyVar param_ty (param_tyty->get_ref ());
+	  parameter_types.push_back (param_ty);
+
+	  TypeCheckPattern::Resolve (p.get_pattern ().get (),
+				     param_ty.get_tyty ());
+	}
+      else
+	{
+	  TyTy::TyVar param_ty
+	    = TyTy::TyVar::get_implicit_infer_var (p.get_locus ());
+	  parameter_types.push_back (param_ty);
+
+	  TypeCheckPattern::Resolve (p.get_pattern ().get (),
+				     param_ty.get_tyty ());
+	}
+    }
+
+  // we generate an implicit hirid for the closure args
+  HirId implicit_args_id = mappings->get_next_hir_id ();
+  TyTy::TupleType *closure_args
+    = new TyTy::TupleType (implicit_args_id, expr.get_locus (),
+			   parameter_types);
+  context->insert_implicit_type (closure_args);
+
+  Location result_type_locus = expr.has_return_type ()
+				 ? expr.get_return_type ()->get_locus ()
+				 : expr.get_locus ();
+  TyTy::TyVar result_type
+    = expr.has_return_type ()
+	? TyTy::TyVar (
+	  TypeCheckType::Resolve (expr.get_return_type ().get ())->get_ref ())
+	: TyTy::TyVar::get_implicit_infer_var (expr.get_locus ());
+
+  // resolve the block
+  Location closure_expr_locus = expr.get_expr ()->get_locus ();
+  TyTy::BaseType *closure_expr_ty
+    = TypeCheckExpr::Resolve (expr.get_expr ().get ());
+  coercion_site (expr.get_mappings ().get_hirid (),
+		 TyTy::TyWithLocation (result_type.get_tyty (),
+				       result_type_locus),
+		 TyTy::TyWithLocation (closure_expr_ty, closure_expr_locus),
+		 expr.get_locus ());
+
+  // generate the closure type
+  infered = new TyTy::ClosureType (ref, id, ident, closure_args, result_type,
+				   subst_refs);
+
+  // FIXME
+  // all closures automatically inherit the appropriate fn trait. Lets just
+  // assume FnOnce for now. I think this is based on the return type of the
+  // closure
+
+  Analysis::RustLangItem::ItemType lang_item_type
+    = Analysis::RustLangItem::ItemType::FN_ONCE;
+  DefId respective_lang_item_id = UNKNOWN_DEFID;
+  bool lang_item_defined
+    = mappings->lookup_lang_item (lang_item_type, &respective_lang_item_id);
+  if (!lang_item_defined)
+    {
+      // FIXME
+      // we need to have a unified way or error'ing when we are missing lang
+      // items that is useful
+      rust_fatal_error (
+	expr.get_locus (), "unable to find lang item: %<%s%>",
+	Analysis::RustLangItem::ToString (lang_item_type).c_str ());
+    }
+  rust_assert (lang_item_defined);
+
+  // these lang items are always traits
+  HIR::Item *item = mappings->lookup_defid (respective_lang_item_id);
+  rust_assert (item->get_item_kind () == HIR::Item::ItemKind::Trait);
+  HIR::Trait *trait_item = static_cast<HIR::Trait *> (item);
+
+  TraitReference *trait = TraitResolver::Resolve (*trait_item);
+  rust_assert (!trait->is_error ());
+
+  TyTy::TypeBoundPredicate predicate (*trait, expr.get_locus ());
+
+  // resolve the trait bound where the <(Args)> are the parameter tuple type
+  HIR::GenericArgs args = HIR::GenericArgs::create_empty (expr.get_locus ());
+
+  // lets generate an implicit Type so that it resolves to the implict tuple
+  // type we have created
+  auto crate_num = mappings->get_current_crate ();
+  Analysis::NodeMapping mapping (crate_num, expr.get_mappings ().get_nodeid (),
+				 implicit_args_id, UNKNOWN_LOCAL_DEFID);
+  HIR::TupleType *implicit_tuple
+    = new HIR::TupleType (mapping,
+			  {} // we dont need to fill this out because it will
+			     // auto resolve because the hir id's match
+			  ,
+			  expr.get_locus ());
+  args.get_type_args ().push_back (std::unique_ptr<HIR::Type> (implicit_tuple));
+
+  // apply the arguments
+  predicate.apply_generic_arguments (&args);
+
+  // finally inherit the trait bound
+  infered->inherit_bounds ({predicate});
 }
 
 bool
@@ -1630,6 +1754,168 @@ TypeCheckExpr::resolve_operator_overload (
   return true;
 }
 
+HIR::PathIdentSegment
+TypeCheckExpr::resolve_possible_fn_trait_call_method_name (
+  const TyTy::BaseType &receiver)
+{
+  // Question
+  // do we need to probe possible bounds here? I think not, i think when we
+  // support Fn traits they are explicitly specified
+
+  // FIXME
+  // the logic to map the FnTrait to their respective call trait-item is
+  // duplicated over in the backend/rust-compile-expr.cc
+  for (const auto &bound : receiver.get_specified_bounds ())
+    {
+      bool found_fn = bound.get_name ().compare ("Fn") == 0;
+      bool found_fn_mut = bound.get_name ().compare ("FnMut") == 0;
+      bool found_fn_once = bound.get_name ().compare ("FnOnce") == 0;
+
+      if (found_fn)
+	{
+	  return HIR::PathIdentSegment ("call");
+	}
+      else if (found_fn_mut)
+	{
+	  return HIR::PathIdentSegment ("call_mut");
+	}
+      else if (found_fn_once)
+	{
+	  return HIR::PathIdentSegment ("call_once");
+	}
+    }
+
+  // nothing
+  return HIR::PathIdentSegment ("");
+}
+
+bool
+TypeCheckExpr::resolve_fn_trait_call (HIR::CallExpr &expr,
+				      TyTy::BaseType *receiver_tyty,
+				      TyTy::BaseType **result)
+{
+  // we turn this into a method call expr
+  HIR::PathIdentSegment method_name
+    = resolve_possible_fn_trait_call_method_name (*receiver_tyty);
+  if (method_name.is_error ())
+    return false;
+
+  auto candidates = MethodResolver::Probe (receiver_tyty, method_name);
+  if (candidates.empty ())
+    return false;
+
+  if (candidates.size () > 1)
+    {
+      RichLocation r (expr.get_locus ());
+      for (auto &c : candidates)
+	r.add_range (c.candidate.locus);
+
+      rust_error_at (
+	r, "multiple candidates found for function trait method call %<%s%>",
+	method_name.as_string ().c_str ());
+      return false;
+    }
+
+  if (receiver_tyty->get_kind () == TyTy::TypeKind::CLOSURE)
+    {
+      const TyTy::ClosureType &closure
+	= static_cast<TyTy::ClosureType &> (*receiver_tyty);
+      closure.setup_fn_once_output ();
+    }
+
+  auto candidate = *candidates.begin ();
+  rust_debug_loc (expr.get_locus (),
+		  "resolved call-expr to fn trait: {%u} {%s}",
+		  candidate.candidate.ty->get_ref (),
+		  candidate.candidate.ty->debug_str ().c_str ());
+
+  // Get the adjusted self
+  Adjuster adj (receiver_tyty);
+  TyTy::BaseType *adjusted_self = adj.adjust_type (candidate.adjustments);
+
+  // store the adjustments for code-generation to know what to do which must be
+  // stored onto the receiver to so as we don't trigger duplicate deref mappings
+  // ICE when an argument is a method call
+  HirId autoderef_mappings_id = expr.get_mappings ().get_hirid ();
+  context->insert_autoderef_mappings (autoderef_mappings_id,
+				      std::move (candidate.adjustments));
+  context->insert_receiver (expr.get_mappings ().get_hirid (), receiver_tyty);
+
+  PathProbeCandidate &resolved_candidate = candidate.candidate;
+  TyTy::BaseType *lookup_tyty = candidate.candidate.ty;
+  NodeId resolved_node_id
+    = resolved_candidate.is_impl_candidate ()
+	? resolved_candidate.item.impl.impl_item->get_impl_mappings ()
+	    .get_nodeid ()
+	: resolved_candidate.item.trait.item_ref->get_mappings ().get_nodeid ();
+
+  if (lookup_tyty->get_kind () != TyTy::TypeKind::FNDEF)
+    {
+      RichLocation r (expr.get_locus ());
+      r.add_range (resolved_candidate.locus);
+      rust_error_at (r, "associated impl item is not a method");
+      return false;
+    }
+
+  TyTy::BaseType *lookup = lookup_tyty;
+  TyTy::FnType *fn = static_cast<TyTy::FnType *> (lookup);
+  if (!fn->is_method ())
+    {
+      RichLocation r (expr.get_locus ());
+      r.add_range (resolved_candidate.locus);
+      rust_error_at (r, "associated function is not a method");
+      return false;
+    }
+
+  // fn traits only support tuple argument passing so we need to implicitly set
+  // this up to get the same type checking we get in the rest of the pipeline
+
+  std::vector<TyTy::TyVar> call_args;
+  for (auto &arg : expr.get_arguments ())
+    {
+      TyTy::BaseType *a = TypeCheckExpr::Resolve (arg.get ());
+      call_args.push_back (TyTy::TyVar (a->get_ref ()));
+    }
+
+  // crate implicit tuple
+  HirId implicit_arg_id = mappings->get_next_hir_id ();
+  Analysis::NodeMapping mapping (mappings->get_current_crate (), UNKNOWN_NODEID,
+				 implicit_arg_id, UNKNOWN_LOCAL_DEFID);
+
+  TyTy::TupleType *tuple
+    = new TyTy::TupleType (implicit_arg_id, expr.get_locus (), call_args);
+  context->insert_implicit_type (implicit_arg_id, tuple);
+
+  std::vector<TyTy::Argument> args;
+  TyTy::Argument a (mapping, tuple,
+		    expr.get_locus () /*FIXME is there a better location*/);
+  args.push_back (std::move (a));
+
+  TyTy::BaseType *function_ret_tyty
+    = TyTy::TypeCheckMethodCallExpr::go (fn, expr.get_mappings (), args,
+					 expr.get_locus (), expr.get_locus (),
+					 adjusted_self, context);
+  if (function_ret_tyty == nullptr
+      || function_ret_tyty->get_kind () == TyTy::TypeKind::ERROR)
+    {
+      rust_error_at (expr.get_locus (),
+		     "failed check fn trait call-expr MethodCallExpr");
+      return false;
+    }
+
+  // store the expected fntype
+  context->insert_operator_overload (expr.get_mappings ().get_hirid (), fn);
+
+  // set up the resolved name on the path
+  resolver->insert_resolved_name (expr.get_mappings ().get_nodeid (),
+				  resolved_node_id);
+
+  // return the result of the function back
+  *result = function_ret_tyty;
+
+  return true;
+}
+
 bool
 TypeCheckExpr::validate_arithmetic_type (
   const TyTy::BaseType *tyty, HIR::ArithmeticOrLogicalExpr::ExprType expr_type)
diff --git a/gcc/rust/typecheck/rust-hir-type-check-expr.h b/gcc/rust/typecheck/rust-hir-type-check-expr.h
index bf36e19..3ac8c4d 100644
--- a/gcc/rust/typecheck/rust-hir-type-check-expr.h
+++ b/gcc/rust/typecheck/rust-hir-type-check-expr.h
@@ -103,6 +103,13 @@ protected:
 			     HIR::OperatorExprMeta expr, TyTy::BaseType *lhs,
 			     TyTy::BaseType *rhs);
 
+  bool resolve_fn_trait_call (HIR::CallExpr &expr,
+			      TyTy::BaseType *function_tyty,
+			      TyTy::BaseType **result);
+
+  HIR::PathIdentSegment
+  resolve_possible_fn_trait_call_method_name (const TyTy::BaseType &receiver);
+
 private:
   TypeCheckExpr ();
 
diff --git a/gcc/rust/typecheck/rust-hir-type-check.h b/gcc/rust/typecheck/rust-hir-type-check.h
index de3467b..d785835 100644
--- a/gcc/rust/typecheck/rust-hir-type-check.h
+++ b/gcc/rust/typecheck/rust-hir-type-check.h
@@ -70,6 +70,8 @@ public:
     return item.trait_item;
   }
 
+  TyTy::FnType *get_context_type ();
+
 private:
   union Item
   {
diff --git a/gcc/rust/typecheck/rust-tyctx.cc b/gcc/rust/typecheck/rust-tyctx.cc
index 2d9051f..34b60b3 100644
--- a/gcc/rust/typecheck/rust-tyctx.cc
+++ b/gcc/rust/typecheck/rust-tyctx.cc
@@ -154,5 +154,37 @@ TypeCheckContext::peek_context ()
   return return_type_stack.back ().first;
 }
 
+// TypeCheckContextItem
+
+TyTy::FnType *
+TypeCheckContextItem::get_context_type ()
+{
+  auto &context = *TypeCheckContext::get ();
+
+  HirId reference = UNKNOWN_HIRID;
+  switch (get_type ())
+    {
+    case ITEM:
+      reference = get_item ()->get_mappings ().get_hirid ();
+      break;
+
+    case IMPL_ITEM:
+      reference = get_impl_item ().second->get_mappings ().get_hirid ();
+      break;
+
+    case TRAIT_ITEM:
+      reference = get_trait_item ()->get_mappings ().get_hirid ();
+      break;
+    }
+
+  rust_assert (reference != UNKNOWN_HIRID);
+
+  TyTy::BaseType *lookup = nullptr;
+  bool ok = context.lookup_type (reference, &lookup);
+  rust_assert (ok);
+  rust_assert (lookup->get_kind () == TyTy::TypeKind::FNDEF);
+  return static_cast<TyTy::FnType *> (lookup);
+}
+
 } // namespace Resolver
 } // namespace Rust
diff --git a/gcc/rust/typecheck/rust-tyty-cmp.h b/gcc/rust/typecheck/rust-tyty-cmp.h
index cc8a180..23e52d9 100644
--- a/gcc/rust/typecheck/rust-tyty-cmp.h
+++ b/gcc/rust/typecheck/rust-tyty-cmp.h
@@ -871,6 +871,29 @@ public:
     ok = true;
   }
 
+  void visit (const ClosureType &type) override
+  {
+    if (base->get_def_id () != type.get_def_id ())
+      {
+	BaseCmp::visit (type);
+	return;
+      }
+
+    if (!base->get_parameters ().can_eq (&type.get_parameters (), false))
+      {
+	BaseCmp::visit (type);
+	return;
+      }
+
+    if (!base->get_result_type ().can_eq (&type.get_result_type (), false))
+      {
+	BaseCmp::visit (type);
+	return;
+      }
+
+    ok = true;
+  }
+
 private:
   const BaseType *get_base () const override { return base; }
   const ClosureType *base;
diff --git a/gcc/rust/typecheck/rust-tyty-rules.h b/gcc/rust/typecheck/rust-tyty-rules.h
index 40e7c44..fe654ca 100644
--- a/gcc/rust/typecheck/rust-tyty-rules.h
+++ b/gcc/rust/typecheck/rust-tyty-rules.h
@@ -624,7 +624,45 @@ class ClosureRules : public BaseRules
 public:
   ClosureRules (ClosureType *base) : BaseRules (base), base (base) {}
 
-  // TODO
+  void visit (InferType &type) override
+  {
+    if (type.get_infer_kind () != InferType::InferTypeKind::GENERAL)
+      {
+	BaseRules::visit (type);
+	return;
+      }
+
+    resolved = base->clone ();
+    resolved->set_ref (type.get_ref ());
+  }
+
+  void visit (ClosureType &type) override
+  {
+    if (base->get_def_id () != type.get_def_id ())
+      {
+	BaseRules::visit (type);
+	return;
+      }
+
+    TyTy::BaseType *args_res
+      = base->get_parameters ().unify (&type.get_parameters ());
+    if (args_res == nullptr || args_res->get_kind () == TypeKind::ERROR)
+      {
+	BaseRules::visit (type);
+	return;
+      }
+
+    TyTy::BaseType *res
+      = base->get_result_type ().unify (&type.get_result_type ());
+    if (res == nullptr || res->get_kind () == TypeKind::ERROR)
+      {
+	BaseRules::visit (type);
+	return;
+      }
+
+    resolved = base->clone ();
+    resolved->set_ref (type.get_ref ());
+  }
 
 private:
   BaseType *get_base () override { return base; }
diff --git a/gcc/rust/typecheck/rust-tyty.cc b/gcc/rust/typecheck/rust-tyty.cc
index 366de80..342fa76 100644
--- a/gcc/rust/typecheck/rust-tyty.cc
+++ b/gcc/rust/typecheck/rust-tyty.cc
@@ -27,6 +27,7 @@
 #include "rust-substitution-mapper.h"
 #include "rust-hir-trait-ref.h"
 #include "rust-hir-type-bounds.h"
+#include "rust-hir-trait-resolve.h"
 #include "options.h"
 
 namespace Rust {
@@ -200,6 +201,7 @@ BaseType::bounds_compatible (const BaseType &other, Location locus,
 	  rust_error_at (r,
 			 "bounds not satisfied for %s %<%s%> is not satisfied",
 			 other.get_name ().c_str (), missing_preds.c_str ());
+	  // rust_assert (!emit_error);
 	}
     }
 
@@ -1672,7 +1674,9 @@ ClosureType::accept_vis (TyConstVisitor &vis) const
 std::string
 ClosureType::as_string () const
 {
-  return "TODO";
+  std::string params_buf = parameters->as_string ();
+  return "|" + params_buf + "| {" + result_type.get_tyty ()->as_string ()
+	 + "} {" + raw_bounds_as_string () + "}";
 }
 
 BaseType *
@@ -1699,8 +1703,10 @@ ClosureType::is_equal (const BaseType &other) const
 BaseType *
 ClosureType::clone () const
 {
-  return new ClosureType (get_ref (), get_ty_ref (), ident, id, parameter_types,
-			  result_type, clone_substs (), get_combined_refs ());
+  return new ClosureType (get_ref (), get_ty_ref (), ident, id,
+			  (TyTy::TupleType *) parameters->clone (), result_type,
+			  clone_substs (), get_combined_refs (),
+			  specified_bounds);
 }
 
 BaseType *
@@ -1717,6 +1723,52 @@ ClosureType::handle_substitions (SubstitutionArgumentMappings mappings)
 }
 
 void
+ClosureType::setup_fn_once_output () const
+{
+  // lookup the lang items
+  auto fn_once_lang_item = Analysis::RustLangItem::ItemType::FN_ONCE;
+  auto fn_once_output_lang_item
+    = Analysis::RustLangItem::ItemType::FN_ONCE_OUTPUT;
+
+  DefId trait_id = UNKNOWN_DEFID;
+  bool trait_lang_item_defined
+    = mappings->lookup_lang_item (fn_once_lang_item, &trait_id);
+  rust_assert (trait_lang_item_defined);
+
+  DefId trait_item_id = UNKNOWN_DEFID;
+  bool trait_item_lang_item_defined
+    = mappings->lookup_lang_item (fn_once_output_lang_item, &trait_item_id);
+  rust_assert (trait_item_lang_item_defined);
+
+  // resolve to the trait
+  HIR::Item *item = mappings->lookup_defid (trait_id);
+  rust_assert (item->get_item_kind () == HIR::Item::ItemKind::Trait);
+  HIR::Trait *trait = static_cast<HIR::Trait *> (item);
+
+  Resolver::TraitReference *trait_ref
+    = Resolver::TraitResolver::Resolve (*trait);
+  rust_assert (!trait_ref->is_error ());
+
+  // resolve to trait item
+  HIR::TraitItem *trait_item
+    = mappings->lookup_trait_item_defid (trait_item_id);
+  rust_assert (trait_item != nullptr);
+  rust_assert (trait_item->get_item_kind ()
+	       == HIR::TraitItem::TraitItemKind::TYPE);
+  std::string item_identifier = trait_item->trait_identifier ();
+
+  // setup associated types  #[lang = "fn_once_output"]
+  Resolver::TraitItemReference *item_reference = nullptr;
+  bool found = trait_ref->lookup_trait_item_by_type (
+    item_identifier, Resolver::TraitItemReference::TraitItemType::TYPE,
+    &item_reference);
+  rust_assert (found);
+
+  // setup
+  item_reference->associated_type_set (&get_result_type ());
+}
+
+void
 ArrayType::accept_vis (TyVisitor &vis)
 {
   vis.visit (*this);
diff --git a/gcc/rust/typecheck/rust-tyty.h b/gcc/rust/typecheck/rust-tyty.h
index 998ed63..9a9f0aa 100644
--- a/gcc/rust/typecheck/rust-tyty.h
+++ b/gcc/rust/typecheck/rust-tyty.h
@@ -1626,31 +1626,35 @@ class ClosureType : public BaseType, public SubstitutionRef
 {
 public:
   ClosureType (HirId ref, DefId id, RustIdent ident,
-	       std::vector<TyVar> parameter_types, TyVar result_type,
+	       TyTy::TupleType *parameters, TyVar result_type,
 	       std::vector<SubstitutionParamMapping> subst_refs,
-	       std::set<HirId> refs = std::set<HirId> ())
+	       std::set<HirId> refs = std::set<HirId> (),
+	       std::vector<TypeBoundPredicate> specified_bounds
+	       = std::vector<TypeBoundPredicate> ())
     : BaseType (ref, ref, TypeKind::CLOSURE, ident, refs),
       SubstitutionRef (std::move (subst_refs),
 		       SubstitutionArgumentMappings::error ()),
-      parameter_types (std::move (parameter_types)),
-      result_type (std::move (result_type)), id (id)
+      parameters (parameters), result_type (std::move (result_type)), id (id)
   {
     LocalDefId local_def_id = id.localDefId;
     rust_assert (local_def_id != UNKNOWN_LOCAL_DEFID);
+    inherit_bounds (specified_bounds);
   }
 
   ClosureType (HirId ref, HirId ty_ref, RustIdent ident, DefId id,
-	       std::vector<TyVar> parameter_types, TyVar result_type,
+	       TyTy::TupleType *parameters, TyVar result_type,
 	       std::vector<SubstitutionParamMapping> subst_refs,
-	       std::set<HirId> refs = std::set<HirId> ())
+	       std::set<HirId> refs = std::set<HirId> (),
+	       std::vector<TypeBoundPredicate> specified_bounds
+	       = std::vector<TypeBoundPredicate> ())
     : BaseType (ref, ty_ref, TypeKind::CLOSURE, ident, refs),
       SubstitutionRef (std::move (subst_refs),
 		       SubstitutionArgumentMappings::error ()),
-      parameter_types (std::move (parameter_types)),
-      result_type (std::move (result_type)), id (id)
+      parameters (parameters), result_type (std::move (result_type)), id (id)
   {
     LocalDefId local_def_id = id.localDefId;
     rust_assert (local_def_id != UNKNOWN_LOCAL_DEFID);
+    inherit_bounds (specified_bounds);
   }
 
   void accept_vis (TyVisitor &vis) override;
@@ -1669,13 +1673,8 @@ public:
 
   bool is_concrete () const override final
   {
-    for (auto &param : parameter_types)
-      {
-	auto p = param.get_tyty ();
-	if (!p->is_concrete ())
-	  return false;
-      }
-    return result_type.get_tyty ()->is_concrete ();
+    return parameters->is_concrete ()
+	   && result_type.get_tyty ()->is_concrete ();
   }
 
   bool needs_generic_substitutions () const override final
@@ -1693,8 +1692,15 @@ public:
   ClosureType *
   handle_substitions (SubstitutionArgumentMappings mappings) override final;
 
+  TyTy::TupleType &get_parameters () const { return *parameters; }
+  TyTy::BaseType &get_result_type () const { return *result_type.get_tyty (); }
+
+  DefId get_def_id () const { return id; }
+
+  void setup_fn_once_output () const;
+
 private:
-  std::vector<TyVar> parameter_types;
+  TyTy::TupleType *parameters;
   TyVar result_type;
   DefId id;
 };